Cathode-ray tube gunsight



Jan. 18, 1949. P. R. WHEELER 2,459,206

CATHODE-RAY TUBE GUNSIGHT Filed Dec 19, 1945 5 Sheets-Sheet 1 PRESENT POSITION I I FUTURE P0s/r/0/v I 2 //7'4RGE mnae'r FUTURE sLAA/r RANGE f \l i i 1.540 ANGLE \PRESENT 51.4w mass 1/ I Luv; 0F F/RE\ )X 0F SIGHT. i v I PRESi/VT LV4770N l l I l FUTURE LEI/A7704! au/v' FIG. 2

ma nus T0 GRAVITY ACTUAL LINE OF F/RE SHELL rmazcmnr l SUPER- ELEVATION /9 A sL,4A/r RANGE (UNCORRECTED LINE OF FIRE) INVENTOR PHIL LIP R WHEEL E I? ATTORNEY Jan. 18, 1949. P. R. WHEELER CATHODE-RAY TUBE GUNSIGHT 5 Sheets-sheaf? Filed Dec. 19, 1945 II-nu- I. r1 IIIIIIIIIII! rl/lr/lI/llllr INVENTOR R. WHEELER PH/L LIP IIIIIIII'I'IIIIIIIIII ATTORNEY Jan. 16, 1949'. P. R. WHEELER CATHODE-RAY TUBE GUNSIGHT 5 Sheets-Sheet 3 Filed Dec. 19, 1945 INVENTOR PHILLIP R. WHEELER ATTORNEY Jan. 18', 1949. P. R.,WHEELER CATHODE-RAY TUBE GUNSIGHT 5 Sheets-Sheet 4 Filed Dec. 19, 1945 ATTORNEY Jan. 18, 1949. P. R. WHEELER 2,459,205

CATHODE-RAY TUBE GUNSIGHT Filed Dec. 19,-1945 5 Sheets-Sheet 5 INVENTOR PH/LLl/ R. WHEEL ER /9dx&;

ATTORNEY Patented I8, 1949 UNITED STATES PATENT orncs 2,459,206

a lic tion Dzcglmalbl'lil; 348552?! No. 636,047

(Granted under the act of March 3, 1883, as amended April 30, 1928: 370 0. G. 757) into the field of view of an operator. The present application is a continuation-in-part of my copending United States patent application Serial No. 510,403, entitled Cathode ray gun sight,

and filed in the United States Patent Offlce on a November 15, 1943, now abandoned.

I am aware that the prior art embraces several electrical gun sights which are premised on the disturbed-line-of-sight principle and which utilize one or more electrical indicating instruments for positioning cross hairs in elevation and in azimuth. The intersection of the cross hairs constitutes a sighting reference mark. In firing a gun at a moving target it is necessary to establish a line of sight on the target and so to establish the line of fire that it leads the line of sight by an amount functionally related to target speed and range. This leading is accomplished by the "target velocity corrections of the sight setting. In the absence of these corrections the projectile would pass behind the target.

The corrections to the sight settings in the prior art are made in various ways. The cross-hairs in the sight are connected in some cases to electric meters whose fluctuations are the function of the rate of movement of the gun mount. Other sights have moveable reticles connected mechanically to the gun mount by gearing or cables, or have tiltable mirrors so connected and positioned in the focusing section of the sight so as to cause the reticle to move as desired. In each of these, the members of the sight forming the displaceable reference mark ,have mass and inertia, and are subject to mechanical lag in operation or overcontrol due to inertia. Such sighting devices of the prior art are inaccurate in opera-. tion as a result of the above mentioned defects.

My invention avoids the above mentioned disadvantages and limitations. of the prior art by providing cathode ray tube means for producing an electrically displaceable' reference mark and means normally stationary with respect to the tube means for reflecting the mark into the field of view of the gun-sight operator. My invention resides in the providing of the cathode ray tube 2 means for producing the reference mark and in the combination of that means with the reflecting means. My invention offers a further advantage in that sights in accordance therewith do not require additional arrangements for illuminating the reticle or reference image.

An object of this invention, accordingly, is to avoid the disadvantages and limitations dependent upon the use of prior art gun sights by employing a cathode ray tube to transmit the sight corrections to the gunner.

A further object of this invention isto provide a novel gun sight inwhich a combination of a cathode ray tube and reflecting means is employed to provide an electrically displaceable reference image for the gunner.

Still a further object of the invention is to provide a cathode ray tube gunsight which acts instantaneously and without any substantial loss of time due to transmission or damping of moving elements, or which may be damped electrically by a desired amount.

For a better understanding of the present invention together with other and further objects thereof reference is made to the following speciflcation, to the claims appended thereto and to the accompanying drawings in which:

Fig. 1 comprises a geometrical presentation of the target velocity portion of the fire control problem;

Fig. 2 comprises a geometrical presentation of the superelevation portion of the fire control problem;

Fig. 3 is a perspective view of operative portions of an antiaircraft machine gun and mount show-' ing the cathode ray tube gun sight installed thereon;

Fig. 4 is a view similar to Fig, 3 and showing a gunner using the cathode ray tube sight;

Fig. 5 is a vertical sectional view of my improved cathode ray tube gun sight;

Fig. 6 is a cross-sectional view of another form of my novel cathode ray tube gun sight;

Fig. '7 is a view looking toward the muzzle of a machine un, showing the cathode ray tube sight in position thereon and also showing the rate generators;

Fig. 8 is a side view of the cathode ray tube gun sight mountedon a machine gun;

Fig. 9 is a complete wiring diagram for coupling the rate generators and the superelevation control potentiometer, through amplifiers, to the beam-deflecting plates of the cathode ray tube; and

Fig. 10 is a schematic diagram, partly in block form, showing a similar circuit arrangement for producing and deflecting a circular reference image.

Fig. 1 shows the essential features of the short range antiaircraft fire control prob em. A gun I I is fired at an airplane target l2. At the instant of fire the airplane is on a position called the present position. The gun should be pointed at some later position of the target, called the "future position, such that the projectile will reach the future position at the same time as the target. The angle between the line from the gun to the present target position (or line of sight) and the line from the gun to the future position (or line of fire) is the lead angle. This lead angle has components in elevation and in azimuth. One of the parameters upon which the proper lead angle and sight setting are premised is the component of target velocity in the plane of elevation. Another is the component of target velocity in the azimuthal plane.

The angular velocity of the target as observed from a gun on a stationary platform is the angular movement of the target about the gun per second of time. The time of flight is obviously the time taken by a projectile to reach the target. The total angular motion of the target during the time of flight is approximately equal to the angular velocity of the target at the present position multiplied by the time of flight in seconds. Other quantities involved in the lead-computing fire control problem, such as present and future slant range are approximately labeled in Fig. 1. It will be seen that range or time of flight is a parameter in part determinative of the appropriate lead angle.

If the gun barrel is pointed at the future position of the target without further correction the projectile would then fall below the target because of the downward force of gravity. To compensate for this undesired effect of gravity the gun elevation is increased by an additiona angle herein called the superelevationangle, as illustrated in Fig. 2. The superelevation angle required is dependent upon. (a) the ballistics of the gun and projectile, (b) the time of flight of the projectile to the target. (c) the cosine of the angle of gun elevation. The ballistics for a given gun can be considered constant over short ranges and therefore the superelevation angle is calculated with a reasonable approximation according to the following equation:

superelevation constant K time of flight x cosine of gun elevation.

In gun sights which operate on the disturbedline-of-sight principle the gunner maintains the line of sight on a target by tracking the target and as he does so he manually positions the gun and the sight housing. The required target velocity and superelevation corrections 'fumish a basis for angularly so disturbing the line of sight with respect to the line of fire that when the line of sight is maintained on the target. the line of fire is appropriate to cause a hit to be scored.

In my above-mentioned copending patent application Serial No. 510,403.there is illustrated a complete cathode ray tube gun sight in which an electrically displaceable reference mark provided by a cathode ray tube is reflected into the field of view of a gunner. By aligning theoptical image a of that reference mark with a target the gunner establishes a line of sight. The cathode ray tube V elevation and in train relative to axes on a supporting frame in order to disturb the line of sight with respect to the line of fire by an amount appropriate to introduce the correction for target velocity. In my copending patent application Serial No. 636,045, entitled "Gun sight superelevation control device, filed in the United States Patent Oiiice on December 19, 1945, there is shown a gun sight of the type in which a reference mark is electrically deflected, not only for the purpose of introducing the target velocity corrections, but also for the purpose of introducing the superelevation correction and thus overcoming the undesired effects of gravity. In my copending patent application Serial No. 636,048, entitled Gyroscopically controlled electrical gun sight, filed in the United States Patent Oflice on December 19, 1945 there is shown a system which provides for'the introduction of electrical corrections to compensate for both roll and pitch of the supporting plane on which the gun and sight are supported. In my copending patent application Serial No. 636,046, entitled "Electrical gun sight superelevation and roll correcting device," .flled in the United States Patent Oflice on December 19, 1945, there is disclosed an arrangement for introducing both roll and superelevation corrections. The claims in the instant case are addressed to a combination which may be employed in any one of the sights disclosed in those copending patent applications. For purposes of clarity of description my invention is herein embodied in a gun sightwhich furnishes corrections for target velocity, range (or time of flight) and superelevation only. In the following description it may be assumed that the gun mount is supported on a stable horizontal plane.

Referring now generally to Figs. 3, 4, 5, 6, 9 and 10 there is illustrated, in an automatic compensating gun sighting arrangement, a gun mount enerally indicated by the numeral 13, a gun ll mounted thereon to permit both vertical and horizontal rotative movement of the gun, and a gun sight generally indicated by the numeral l5. This gun sight comprises the following:

Cathode ray tube means I! for providing a sighting reference mark, beam-deflecting means 95, 96, I06 and Ill! (Fig. 9) for positioning the reference mark, means 39, ll actuated by rotative movements of the gun for controllingthe positioning means, thereby to deflect the reference mark in such ratio to the gun motion as to cause the line of fire to lead a moving target I! by an amount which compensates for the speed of the target, and means generally indicated by the numeral I8 and governed by the elevational position of the gun for further controlling the positioning means, thereby to move the reference mark in such manner as to cause the line of fire I! to be elevated with respect to target I2 by an amount which compensates for the effect of gravity on a missile fired from the gun. There are also disclosed means I3, 14, 13', I4; 65 (Fig.

In the drawing (Fig. 5) the cathode ray tube gun sight is designated generally by thenumeral l5 and includes-a cathode ray tube .63, mounted in a cylindrical housing 2| by means of suitable positioningelements 22 and 23. The conductors leading to the cathode ray tube from terminals ll, I44. 3. and ill (Fig. 9) are contained in an insulated cable 24. The cylindrical housin 2| is attached by screws or other suitablemeans to the lower end of the main housing 25 which has an opening at the point of attachment. A plane reflecting mirror 21 is located in the lower end of the housing 25 at an angle of approximately 45 to the horizontal. Pivoted to the upper end of the housing 25, is a semi-reflecting flat glass plate 23, which is inclined at an angle of approximately 45 to the horizontal and which may be lifted upwardly on a pivot for purposes 01' cleaning the inside of housing 25. A suitable catch 29 is provided for holding the glass 28 in position. In the upper end of the rear wall of housing 25 is an opening 30 which provides communication between the interior of housing 25 and the interior of the eye piece support 3 l, which is attached to the housing by means of screws or other suitable means. A rubber eye piece 32 and a peep 33 are mounted on a tube 34 which is slidably mounted in the outer end of the support 3|. The position of tube 34 in the support 3i is adjusted by means of a spring pressed plunger 35 which cooperates with notches 36 on the tube. A knob 31 attached to-the tube serves as a means for moving the tube. A mounting bracket 38 is attached to the lower front wall of the housing 25 to provide means for mounting the unit on a gun.

In order to boresight this unit, mirror 21 is pivotally attached to the side walls of the housing 25 is provided. The screws 4| and 42 are tightened against an arm 45 which turns with the mirror, and by varying the relative positions of the screws 4i and 42 the mirror 21 may be positioned accurately to boresight the gun in elevation. For boresighting in train, the sight is rotated on its supporting member 46 (Fig. 8) which fits into bracket 38. A screw (not shown) or other device for positioning the sight correctly in train may be provided.

The unit shown in Fig. 6 is somewhat similar to that illustrated in Fig. 5, but instead of providing a mirror such as that shown at 21 in Fig. 3, the cathode ray tube 63 is mounted in a vertical position and a collimating lens system is provided above the cathode ray tube at 41 to constitute a collimated sight. I

The cathode ray tube employed in the sight is of any conventional type having suitable electrongun structural elements for projecting an electron beam from its cathode onto a fluorescent screen 50. A deflecting means comprising vertical I06, I01) and horizontal (96, 95) pairs of electrostatic deflecting plates is provided in the tube for deflecting the electron beam as is common In the cathode ray tube of the sight shown in Fig. 5, a mark such as a spot or circle is formed on the screen 50 and is reflected upwardly by mirror 21 and rearwardly by the flat piece of glass 28 to the eye of the gunner positioned behind the rubber eye piece 32. The gunner looking into the sight through the rubber eye piece seesthe image of the spot or circle created by the cathode ray tube and reflected by the optical elements 21, 28 into the sight line and at the same time views the target through this piece of glass 28. The gun is aimed by centering or effectively superimposing the reflected image on the target. By. means of the electrical controls for the cathode ray tube, hereinbelow described, the mark on the tube screen is able to provide various corrections. Movement of the mark on the screen 50 produces a corresponding movement of the image reflected into the gunners line of sight by the optical elements 21, 28 so that a new line of sight is established to enable the gunner to adjust the position of the gun to correspond to the sighting corrections put into the cathode ray tube.

Due to the fact that the line of sight is defined by the image reflected by the optical elements 21, 28 into the operator's field of view and the peep 33 located in the rubber eye piece, the amount of correction oi the line of sight by a given movement of the image depends upon the position oi the peep in the eye piece with relation to mirror 24. The rubber eye piece and peep are shown adjustable so that this correction can be calibrated by movement of the eye piece and peep in and out of the support 3 I.

The collimated type of sight shown in Fig. 6 possesses the advantage that the eye of the gunner need not be in a fixed position relative to the peep as is necessary in the unit shown in Fig. 5. In the Fig. 6 embodiment the mark created on the screen 50 of the cathode ray tube is collimated as in an illuminated sight by means of the lens system 41 (or 48) and focused an infinite distance away. The mark is reflected by the glass plate 28 into the gunners field of view. The device shown in Fig. 6 may be boresighted by adjustment of the bracket 38 and by a simple adjustment of the angle of the semireflecting plate 28.

It will be noted that the optical elements 21 and 28 are normally stationary with respect to the cathode ray tube means l1, The mirrors do not normally move as in the Mark 14 sight nor is the reference image mechanically reflected as in the Alkan sight.

In attaching the cathode ray tube sight to a.

gun. the sight is conventionally placed as near the trunnions of the gun as possible so that the eye of the gunner may remain at approximately the same height for all angles of elevation of the gun. In Fig. 3, the cathode ray unit of the type shown in Fig. 5 is shown mounted on an antiaircrai't machine gun, and in Fig. 4 a gunner is shown with the sight in operation (only the hands and an eye of the gunner being shown).

The sighting arrangement also includes means actuated by rotative movements of the gun for controlling the positioning means included in the cathode ray tube. This electrical means so responsive to dynamic movements of the gun and elevation and in azimuth for displacing the reference mark in'elevation and in azimuth by an amount which is functionally related to the rates of such gun movement, comprises a voltage generator 39 and a voltage generator 44. Generator 39 is mounted on the carriage yoke 52 of the gun mount and is adapted to be actuated by a gear 53 which meshes with a. beveled gear segment 54mounted on the gun carriage. Elevation or depression of the gun causes rotation of the rotor of generator 39, the voltage generated being directly proportional to the rate at which gagement of pinion gear 56 with ring gear 88, and a voltage proportional to the rate of train is generated and applied to a horizontal deflection amplifier and gain (range) control 68 (Fig.

following a target, the value of each voltage being directly propportional to the rates of elevation and train, respectively, of. the gun. These voltages are functionally related to the vertical and horizontal components of the velocity of the target. These voltagesare applied to the amplifiers, there amplified and then applied to the cathode ray tube 63 to control the location of the mark on the screen 58 and thus to define the line. of sight and to control the direction of fire of the gun.

When the sight is used as a rate sight, utilizing the rate generators 39 and 44, it is essential that the voltages applied to the amplifier be varied in accordance with range or time of flight. This is extremely important due to the fact that the angular rate of movement of the gun in following a target traveling at a given linear velocity with respect to the gun varies inversely as the range. Assuming that the projectile velocity remains constant for all ranges for any given target speed relative to the gun, the lead angle remains constant for all ranges. In order to prevent the increased angular rate of movement of the gun for a near target from deflecting the reference mark excessively and giving too large a lead angle, the amount of deflection of the mark for a givenrate of angular movement of the gun must be decreased as the range decreases.

This change in the amount of deflection of the mark is accomplished by means of elements 'I3'I4 and 'I3'I4 in units 68 and 68, respectively (Fig;'9). Range. settings are put into the amplifier by manual adjustment of a range setting control comprising ganged sliding contacts ll and 1.!

Although it was assumed in the preceding paragraph that the projectile velocity remains constant for all ranges, this is, of course, not entirely true. Decreasing projectile velocity with increased range is a factor which should be considered in a rate sight. As the range increases, the average-velocity of the projectile decreases and the lead angle must be increased slightly with increased range to compensate for this loss of projectile velocity. This correction is sometimes called a time of flight correction and should be considered in the range setting device just discussed. As is obvious-to those skilled in the art, this is accomplished by appropriate shaping of resistor 13 and 13', as suggested at lines 108 to 111, page 2, of United States Patent No. 1,322,153, issued to J. S. Wilson and W. E.-Dalby, on November 18, 1919. Thus the final correction made in the position of the reference image in the sight by the adjustment of the. range control 7 so, u, 14' is functionally related'to time of flight,

arly with the range The sighting arrangement also includes a superelevation potentiometer I8 (Fig. 8). There I 8 have already been described arrangements for so disturbing the line of sight as to introduce corrections for target velocity and range. However. the solution oi the problem posed in Fi 2 requires a superelevation control for applying to the disturbing means (deflecting plates I08 and I81, Fig. 9), through the amplifyingunit 68', an electrical signal having a magnitude trigonometrically functionally related to the angle of elevation of thegun, thereby to cause the electrostatic plates I" and III! to disturb the reference mark and the line of sight by an amount trigonometrically functionally related (as the cosine) to the angle of elevation. When such a superelevation control is provided, the maintenance of the line of sight on a target causes the line of flre to be angularly elevated with respect to the line of sight by'the amount of the desired superelevation correction. The means for supplying the superelevation correction comprises a potentiometer I8. The electrical details of the potentiometer I8 are shown in Fig. 9 and its operation is hereinabelow described. It sliding contact 66 (Fig. 9) is positioned by a linkage 68 secured to the carriage yoke 52. The housing portion 58 of the potentiometer contains the resistor 61 (Fig. 9) and is secured to the gun, so that it moves in elevation with the gun. Movement of the gun in elevation causes movement of the linkage 59 and appropriate movement (hereinbelow described) of sliding contact 66 in potentiometer I8. Potentiometer I8 and linkage 59 are so arranged that when the gun is on the true horizontal, sliding contact 66 (Fig. 9) is adjacent to terminal 65 and the full voltage output of battery 62 is applied to resistor 64. On the other hand, when the gun is pointed in a vertical direction, contact 66 is effectively connected to the negative terminal of battery 62 and no voltage is applied from the output of potentiometer I8 to resistor 64. Between these two limits, the voltage applied to resistor 64 by battery 62 and potentiometer I8 varies as the cosine of the angle of elevation or depression of the gun and resistor 61 is appropriately shaped to accomplish this objective in a manner indicated in my copending U. S. patent application Serial No. 636,045, filed December 19,

1945, and entitled "Gun sight superelevation control device.

The output signal from potentiometer I8 and the output signal of generator 39 cooperate to cause the vertical position of the reference image to be determined by superelevation as well as by the elevational component of the velocity of the target and range. The eievational position of the reference image is a function of two arguments, the first of these being a rate or dynamic condition and the second beinga position or static condition; Since the superelevation correction isalso functionally related to range, the sum of the outputs of generator 39 and potentiometer I8 is applied to gain control 13', ll of unit 68'.

Referring now speciflcally'to Fig. 9, there is illustrated a complete electrical system for so coupling the train generator 44 and the combination of the elevationgenerator 39 and the superelevation control potentiometer It to the horizontal plates and the vertical beam-deflecting the cathode ray tube screen to be positioned in which, as indicated. does not vary precisely linecoordination with the movements of the gun in sociated input coupling circuit to the train gen- .erator and output coupling circuit to the horizontal beam-deflecting plates of the cathode ray tube, a vertical deflection amplifier and gain (range) control 68' and its associated input plates of the cathode ray tube, and a conventional power supply 69.

Units 68 and 6B are identical in construction and in operation, so that the following detailed description is confined to unit 68, and unit 68' is shown primarily in block form, only a few elements being detailed. All elements of unit 68' shown in detail in Fig. 9 bear the same reference numerals as the corresponding elements of unit 68, with the addition of a prime mark for purposes of facilitating the description thereof. The system comprising unit 68, unit 68', power supply 69 and cathode-ray tube 63 is of the prior art, and the circuits included in those units have been copied from pages 16 and 17 of the unclassified operating instructions book for the Du Mont type 208 cathode-rayoscillograph equipment, published in 1943 by the Allen B. Du Mont Laboratories, Incorporated, Passaic, New Jersey, U. S. A.; this publication being fully identified as DE-246, issue 3. D. C. operation is described at pages 12 and 24 of that book. The circuit is well known to those skilled in the electrical art and is included herein for the sole purpose of insuring against any doubts that it may not be equally well known to those skilled in the gun sight art. It is also shown at page 225 of the book Ultra-High Frequency Techniques, by Brainerd, Koehler, Reich and Woodrufl", published in 1942 by D. Van Nostrand Company, Inc., 250 4th Avenue, New York, New York.

The output terminals of the train generator H, 12 are coupled to a voltage divider 13. This divider with its sliding contact It constitutes a potentiometer or gain (range) control in that it provides for a division of the output signal of the train generator and a choice of the portion of that signal applied to the remaining elements of unit 68 in cascade with this potentiometer. The coupling between the elevation generator and unit 68 is generally similar to the coupling between the train generator and unit 68, appropriate modifications being made because of the fact that unit 68 is controlled both by elevation-lead-angle-correction voltages and superelevation correction voltages. To this end, the output terminals H 12' of the elevation generator are connected in series with a resistor 6t, and the series combination of resistor 66 and the output circuit of generator 39 is coupled to the resistor portion 73' of a potentiometer comprising resistor 13' and sliding contact 16'. The last mentioned sliding contact provides gain (range) control. The sliding contacts It and it are ganged by any suitable expedient indicated by the dashed line 65 in order that the range correction may be simultaneously introduced for both elevation and train signal channels. The voltage across resistor 13 is equal to the sum of the voltage generated by the elevation generator 39 and that appearing in resistor 64. The last-mentioned voltage is equal to the drop between center tap terminal 65 and the sliding contact 56 of the superelevation control potentiometer. tentiometer includes a resistor 61 having a center tap coupled to one terminal of a battery $2 and;

having both of its leads coupled to the other terminal of that battery. The terminals of resistor 84 are individually coupled to sliding contact i8 and the junction of the leads of resistor 61 and the battery 62.

The output voltage of the train generator appearing across resistor 13 is functionally related to the rate of tracking of the target in train or to the horizontal component of target velocity.-

The signal is also functionally related to rangeor time-of-flight by reason of the setting of sliding contact 1%. Similarly, the signal appearing across resistor I3 is a composite of the signal appearing across resistor 64, this signal being functionally related to the elevational position of the gun with respect to the horizontal (superelevation correction) and the signal output of the elevation generator, the last named signal being functionally-related to the rate of tracking of the target in elevation or the vertical component of target velocity. This composite signal is functionally related to range by reason of the adjustment of sliding contact 16'.

The general operation of unit 68 is such as to amplify the signal appearing across resistor 13 to such an extent as to permit that signal to govern the horizontal deflection of the beam of cathode ray tube 63. Similarly the function of unit 68' is to amplify the signal appearing across resistor 73. to such a degree as to permit it to control the vertical deflection of the beam.

Referring now specifically to the signaling circuit of unit 68, the signal appearing between sliding contact I3 and ground is applied to the control electrode of a triode tube 15 6F8G.) Coupled to this control electrode is a grid resistor 16 (one megohm). The cathode is connected to a terminal 19 (at minus 280 volts with respect to ground) through a series combination of resistors Ti and 18 (15,000 ohms potentiometer and 300,000 ohms, respectively). The anode of this tube is coupled to the positive terminal 80 of an appropriate source of space current herein below described (at a potential of plus 155 volts). Tube 15 is arranged as a cathode follower circuit and its output circuit is coupled to the in- This poput circuit of tube M, the control electrode of the latter being connected to a sliding contact 98 on resistor ll. Tubes Bi and 02 (each 6V6) are arranged as a paraphrase amplifier and use phase inversion for the purpose of converting the output signal of tube l5 (which is relatively weak and unbalanced to ground) to a relatively high voltage signal, balanced with respect to ground and applied to the horizontal beam deflecting elements of tube 53 in such a manner as to minimize undesired defocusing. To this end the cathodes of tube 8! and tube 82 are connected, their common terminal 84 is connected to ground through a resistor 83 (400 ohms) and the control electrode of tube 82 is grounded. The output signal from tube 15 is employed to drive tube 8! and this signal is of such a polarity as to be a degenerative signal with respect to tube 82. The input circuits of tubes 8| and 82 are so proportioned that the voltage effective between grid and cathode of tube 82 is approximately half of the input voltage applied to the combination of tubes 88 and 82 from tube 15. Similarly, the voltage eflective between grid and cathode of tube 8! is also approximately half of that input voltage. Thus the input voltages of tubes 8! and 82 are substantially equal but are of opposite.

polarity when referred to their control electrodes, so that the output signals are of approximately the same amplitude but of opposite polarity. The anodes of these tubes are coupled to a terminal 89 (plus 280 volts) through two series combinations individually comprising resistor 85 and choke 81 (25,000 ohms and 7-19 millihenries, respectively) and resistor 88 and choke 88 (25,000 ohms and Z19 millihenries, respectively). Screen potential is supplied from terminal 89 to the screen grids of these two tubes 8| and 82 by connecting the junction of these screen grids through a resistor 88 (150,000 ohms)- to terminal 89. The anodes of the tubes 8| and 82 are individually coupled through individual parallel combinations of resistor 9| and condenser 82 (750,000 ohms and 0.25 microfarad, respectively) and resistor 93 and condenser 84 (750,000 ohms and 0.25 microfarad, respectively) to the horizontal beam deflecting plate 85 and 88 of tube 68.

As is well known to those skilled in the art the general operation of and cooperation between units 68 and 83 is such that when the signal appearing in resistor '73 becomes more positive with respect to ground, plate 95 becomes more negative and plate 96 becomes more positive, with the result that the spot provided by the electron beam of tube 63 is moved to the right. Similarly, when the signal appearing across resistor 78 is of negative polarity with respect to ground the spot is deflected toward plate 95. The average direct current voltages of the plates of tubes 8| and 82 act as electron beam-positioning voltages, since there are no blocking capacitators to keep these potentials off the deflecting plates 85 and 88.

The sliding contact 88 on resistor 11 acts as a positioning control or spotting control. When this sliding contact is moved upwardly toward the cathode of tube 15, it will be assumed that the potential of the grid of tube 8| is given a positive increment. This increment is amplified and shifted in phase by 180 degrees by tube 8|, appearing at its plate as a change in potential equal to the amplification of the stage multiplied by the original increment. In this manner the potential of the deflection plate 95 becomes more negative and repels the electron beam. At the same time a positive amplified change in potential appears at the plate of tube 82, thus making the cathode ray tube deflection plate 98 more positive by that amount and that plate attracts the electron beam toward it. The average potential of the space between the deflection plates has been maintained constant, but the fluorescent spot has assumed a new position on the cathode ray tube screen. Signal potentials from the train generator are then superimposed upon the steady positioning potential to deflect the spot with reference to the 'base position so established. When the polarity of the signal applied to resistor I3 is reversed, the direction of deflection is also reversed.

The cathode follower I is so designed that there is a point about the middle 01 the potentiometer comprising resistor H at which the voltage to ground is zero. This is practicable because the anode of that tube is connected to terminal 80 and the cathode is connected through a set of load resistors to terminal I8. When the position-control sliding contact 98 is set at the ground potential point, the bias on tube 8| must be the same as the bias on tube 82. If no signal is applied, both of those tubes conduct the same amount of current and the voltage at the plate of tube 8| is the same as the voltage at the plate of tube 82. The spot will then be in the center of the screen if the electron gun of tube 88 is properly aimed.

If it is desired to move the spot in one direction in order to establish a reference position about which the output signals of the train generator prod: :e variations, the sliding contact on resistor 11 is moved upwardly, say, so that the grid of tube 8! becomes more positive with respect to ground. This causes tube 8| to have a larger average current and the cathodes of tubes 8| and 82 tend to become more positive. However, when the cathode of tube 82 becomes more positive, the bias on this tube is increased and it passes a smaller current. This tends to reduce the voltage drop across the common cathode resistor 82, but the result is that the voltage across resistor 88 will be larger than it was when the grid of tube 8| was at ground potential. Therefore, since tube 8| is passing a larger current than before, and tube 82 in passing a smaller current, the average voltage at the plate of tube 82 will be more positive than the voltage at the plate of tube 8|, and the spot is attracted at the right toward deflecting plate 88. In a similar way, it is obvious that the spot will move to the left or toward deflecting plate 85, if the position control 98 is so moved as to make the grid of tube 8| more nega-- tive with respect to ground. Movement of the position control 88 has very little effect on the gain of tubes 8| and 82, since the actual shift of bias is so small that the tubes still work on the linear portions of their characteristics. The overall gain is slightly aifected because the amplitude of the input signal to tube 8| varies somewhat as the sliding contact 98 on resistor 11 is moved. However, since resistor 18 is large compared to resistor 11'', most of the signal voltage is developed across resistor 18. Thus the overall gain is decreased or increased approximately one per cent. Since the voltage change which appears across resistors 8| and 83 when the position control 88 is moved, is only about 10 per cent of the change in voltage at the plates of tubes BI and 82, capacitors 82 and 83 can change their charge so rapidly that the lag between the adjustment of control 88 and the assumption of a new position by the spot on the cathode ray tube is not noticeable.

In my co-pending U. S. Patent application, Serial Number 627,515, filed in the U. S. Patent Oflice on November 8, 1945, and entitled Electrical control device, there is shown a novel combination of two potentiometers for centering control of a cathode ray tube beam. One of these potentiometers may be used as resistor TI and position control 98 in unit 68, and the other of these potentiometers can be used as resistor 11' and position control 88' (not shown) included in unit 68.

The power supply 68 furnishes biasing and the tube filament-heating potentials for units 68, 88', and 88. It comprises a conventional power transformer 0, which has a primary winding coupled through terminals 2 and 3 to a suitable volt, 60 cycle, alternating current source (not shown). The transformer has a secondary winding M4 (6.3 volts) for supplying filamentheating current to the cathode ray tube, as indicated by the letters Z-Z, and a secondary winding 5 (6.3 volts) for furnishing filamentheating current to tubes I5, 8| and 82 as indicated by the letters XX.

In order to provide a potential of 280 volts above ground, which potential is applied to terminals 88 and 88' and to the intensifier electrode H! of tube 63, there is provided a rectifier circuit com- 13 prising a center-tapped secondary winding portion H8 in transformer H and a full control wave rectifier tube I I 8 (type 80). The center tap is grounded and it comprises the negative terminal of this 280 volt source. The plates are connected to the terminals (if this secondary portion "Land the filament of tube H9 is energized from a center-tapped secondary winding I20 volts). The center tap of winding I constitutes the positive terminal of this voltage source. In order to filter this voltage the center tap of winding I20 is brought out to terminal I23 through a filter network comprising shunt condensers I24, I25 and I28 (40 microiarads, 16

microfarads, and l microfarad respectively) and series chokes I28 and I29 (each 8 henries).

In order to provide a 155 volt regulated potential for application to terminals 80 and 80', 3

terminal I23, at which a'potential of 280 volts (positive with respect to ground) is available, is connected to ground through a series combination comprising theanode-cathode path of'a tube I30 (W6) and resistors I3I and I32 (each 500,000 ohms). In order to provide a negative bias for the control electrode of tube I30 that electrode is connected to the Junction of resistor I34 (500,000 ohms) and the anode of a tube I35. A potential of plus 155 volts is made available atterminal I38 (i. e. the Junction of resistors I34 and I3I). Terminal I38 is connected to terminal 80 and 80' of unit 88 and 88'. In order to stabilize this 155 volt potential there is provided a conventional voltage regulator comprising a pentode tube I35 (68.17) and a neon tube I31 A, watt). The anode-cathode paths of these tubes are connected in series between terminal I38 and ground. The screen grid of tube I35 is connected to terminal I38. The control electrode biasing poten-- the pentode vacuum tube I35. This voltage regulator produces an output of voltage which is independent of fluctuations in the alternating current supply and changes in load over a wide range. The output voltage of this regulator is developed across the resistors I3I and I 32 in parallel with the resistance of the load. These resistors make up the resistance of one part of a total voltage divider. The other resistance, through which all of the load current must fiow, is the plate to cathode resistance of tube I30. The other elements of the circuit are used to control the resistance of tube I30 and therefore, to maintain a constant voltage across the load. The voltage at terminal I36 is the regulated voltage output of the regulator. The potential of the cathode of tube I35 is held at a constant positive value by the neon tube I31. The control grid potential of tube I35 is a voltage selected by the potentiometer comprising resistor I32 and sliding contact I40. This potentiometer is set so that the grid voltage is less positive than the cathode by an amount (the bias) which causes tube I35 to pass a certain plate current. This plate current fiows through the plate load resistance I34 and causes a drop across it. The magnitude of the voltage across resistor I34 is the bias on tube I30. Therefore the adjustment of the potentiometer setting I establishes the 14 normal resistance or tube I30. This adjustment is used to set the value of load voltage which the regulator is to maintain.

If the load voltage tends to rise, whether from 5 a decrease in the load current or from an increase in the input voltage. the voltage on the grid of tube I35 also tends to rise (become less negative) the cathode voltage remaining practically constant. Tube I35 then conducts more current, be-

1 cause the bias is smaller. A greater current flows through resistor I34 which causes a greater voltage drop across this resistor. This voltage, which is the bias voltage for tube I30, causes the plate resistance of tube I30 to increase. A larger por- 15 tion of the available voltage appears across the higher resistance of tube I 30 and the load voltage remains practically constant. The action is reversed as the load voltage tends to fall. The anode of the glow tube I31 is connected to the cathode oi.

20 tube I 35 and to the regulator voltage output terminal I38 through resistor I38 (100,000 ohms). It is necessary to connect the glow tube to the high potential terminal I38 in this manner in order to cause the gas in this tube to ionize when the power 25 supply is first to turn on. All of the load current must pass through tube I30. For this reason this tube must be capable of passing a large current. Addition of the condenser I4I increases the fraction of the voltage change impressed upon the grid 3 of tube I35 when the change occurs rapidly. It

the reactance of this condenser at ripple frequency is small in comparison with the resistance which it shunts, the condenser appreciably, increases the ability of the circuit to reduce the ripple.

35 Voltage regulators of this general-type are fully described in "The Theory and Applications of Electron Tubes, by Herbert J. Reich, second edition. McGraw Hill Book Company, New York,

1844, section 14-l3, pages 590 to 594, and in the 40 publication Radio Engineers Handbook, by

Frederick E. Terman, first edition, McGraw Hill 4 Book Company,New York, 1943, section 8, paragraph 9, pages 614 to 617.

It is also necessary to make available for appli- 4 cation to terminals I9 and 19' a potential of 5 -nal of winding I I8 constitutes the positive terminal of this potential source and the junction of the cathodes of tube I44 is connected to one lead of winding I I8. For filtering purposes there is provided a combination of series resistor I45 (47.-

000 ohms) and shunt condensers I48 and I48 (1 microfarad and 16V microfarads, respectively).

The terminal of resistor I45 remote from tube I44 I is brought out to an output terminal I49 and that terminal is connected to terminals I9 and I8 0! 00 units 68 and 58"respectively.

Filament potentials (5 volts) for tubes I 30 and I35 are provided by a secondary winding I5I on transformer III) as indicated by the letters Y-Y.

There remains to be described the high potential source for the anodes of the cathode ray tube '63. As is conventional in tubes of this type the second or accelerating anode I53 is grounded so that it is necessary to bias the cathode I54 negatively with respect to ground so that the anodes are eflectively biased positively with respect to the cathode. Therefore, there is provided a high potential rectifier comprising that portion of winding II8 between grounded terminal I56 and lead I 58 and a rectifier tube I53 (type 80), the plates I of tube being connected together and its fila.

1-5 ment being energized from portion I60 of that winding. The junction of the plates constitutes the negative lead of this potential source (minus 1,100 volts) and this junction is brought out through resistor I64 to terminal I62. Filtering is provided by a shunt condenser I63 (0.5 microfarad) and a series resistor I64 (50,000 ohms) so that there is available at terminal I62 a potential of approximately minus 1,050 volts. Terminal I62 is also connected to terminal I05 and I05 01' units 68 and 68', respectively.

All of the potential sources for units 66 and 68' have now been described and there remains to be described the arrangement by which the electron-gun electrodes of the cathode ray tube are excited. There is arranged between terminal I62 and ground a conventional bleeder resistor comprising four individual resistors I66, I61, I66, and I69 (100,000 ohms potentiometer, 200,000 ohms, 500,000 ohms potentiometer, and 1 megohm, respectively). The cathode is connected to potentiometer I66 by a sliding contact I which serves as a spot intensity control. The brilliancy control electrode I1I is coupled to terminal I62, filtering being provided by a combination of shunt condenser I12 (0.1 microfarad) and a series resistor I13 00,000 ohms). Movement'oi sliding contact I10 varies the positive bias of cathode I54 with respect to the brilliancy control electrode HI and therefore varies the intensity of the spot on the tube-screen. The focusing anode I15 is positively biased with respect to the cathode by connection througna sliding contact I16 to potentiometer I68. Contact I16 serves as a focusing control. Since the accelerating anode I53 is grounded it is effectively connected to the ground terminal of resistor I66 and is therefore highly positively biased with respect to the oathode. The intensifier electrode I I1 is coupled to the plus 280 volt terminal I23 and is therefore still more highly positively biased with respect to the cathode.

It is desirable that the junction of terminal 99 and resistors 93 and I03 be at a lowerpotential than plus 280 volts. It is also desirable that the junction of terminal I00 and resistors 0| and IOI be at a lower potential than plus 280 volts. These desirable conditions should exist when no signal outputs are being taken from train generator 06 and elevation generator 39. Accordingly the minus 1050 volt terminal I05 is connected to the junction of the resistors I02 and I04. In passing from terminal I05 to terminal 69 through resistor I 04, resistor I03, resistor 63, resistor 66, and choke 88. the potential increases from minus 1050 volts to 280 volts. Similarly, in passing from terminal I05 to terminal 69 through elements I02, IOI, 9|, 85 and 81 a similar increase in potential is provided. Thus the two above-mentioned objectives are accomplished.

A cathode ray tube having an electron gun structure and post-deflection acceleration means is fully described on page 342 of the above-mentioned publication by Terman and is old in the cathode ray tube art.

The operation of the circuit disclosed in Fig. 9 is well known to those skilled in the cathode ray tube art and a detailed description thereof is not necessary. Briefly, however, it will be assumed under a particular condition that the train generator output signal is of positive polarity. The

ultimate effect of this signal on the position of the spot between plates 06 and 66 is considered. This s gnal is applied to the input circuit of tube 16 The cathode of tube 16 follows the grid potential andsliding contact 66, under the assumed condition, becomes more positive with respect to ground so that a signal of positive polarity is applied to tube 6|. This signal is of negative polarity as applied to tube 62. Tubes BI and 62 shift the applied signal in phase by 180 so that the plate of 6| becomes more negative and that of 62 more positive. The result is that terminal I00 -nd beam deflecting plate 05 become more negative and repel the cathode ray tube beam, while terminal 99 and deflecting plate 66 become more positive and attract the cathode ray tube beam. The spot provided by the beam is therefore deflected or moved to the right. This is the case when the gunner is tracking a target which has a velocity component toward the left. The

amount of the deflection is functionally related to target velocity, since it is functionally related to the magnitude of the output signal of the train generator. Additionally, the beam displacement is related to range, since it is determined in part by the setting of gain control 14. Thus the positions of the spot and the reticle it provides are determined in accordance with the ballistic corrections required. As range increases the sliding contact 14 on the gain control should be moved away from ground. For purposes of spotting corrections the position control 66 is employed.

The operation of unit 66' and plates I06 and I01 is precisely the same as that of vunit 66 and its associated beam deflecting plates. However, the input signal applied to unit 66 is functionally related to the sum of the output voltage of the elevation generator and the output voltage of the superelevation control potentiometer, the aggregate of those voltages being functionally related to range by reason of the operation of gain control 14. The spot is deflected up or down in ac- .cordance with the rate of ascent or descent of a found in the following publications: Cathode resistor I66.

Ray Tubes and Allied Types," Technical Series TS-2, RCA Mfg. Co., 1110., Harrison, N. J., 1935, pages 78 to inclusive; The Radio Amateurs Handbook, 20th edition, 1943, published by the American Radio Relay League, West Hartford. Conn., pages 52 to 55, inclusive, and pages 396 to 398 inclusive; the above'mentioned publication by Reich, pages 628 to 634, inclusive, particularly page 634, and the above-mentioned publication by Terman, pages 947 to 950, inclusive, particularly page 948. This arrangement is generally similar to that disclosed in Fig. 10 and includes train and elevation generators. a superelevation control potentiometer, and suitable direct current amplifiers I60 and III. Since the electrostat c beam-deflecting pates 06 and I06 are here grounded, amplifiers I60 and I 6| are so designed so as to produce amplified output signals unbalanced to. ground. Amplifier. I60 is coupledto plates 65 and 66 and amplifier I6I is coupled to plates I06 and I01. The amplifiers may include any conventional gain control to provide for.

range adjustment. Inserted between amplifier I60 and plate 66 is a resistor I 02. Similarly arranged between'plate I01 and amplifier Ill is a Time-quadrature alternating current voltages are individually impressed upon these resistors from the separate phases I64 and I06 of a two-phase alternating current generator l7 I86. The time qnadrature voltages from genera tor l86 cause the beam to sweep in a circular pattern and thusto provide a circular reticle. The size of this reticle can be determined by varying the output voltages of generator I86, in various obvious manners well known to those skilled in the art. For xample, the resistors can be employed as potentiometers and their sliding contacts are ganged by any suitable expedient indicated by the dashed line I81. The signals representative of ballistic corrections then displace the circular reticle rather than the spot type of reticle provided by the Fig. 9 circuit. The operation of the Fig. 10 system is otherwise generally similar to that of the Fig. 9 system.

While there have been shown and described what are at present considered to be the preferred embodiments of the present invention it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the true scope of the invention, and it is, accordingly, intended in the appended claims to cover all such changes and modifications as fall within the true scope of the invention and outside of the proper scope of the prior art.

The invention herein described may be manufactured and used by or for the Government of the Umted States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. An automatic compensating gunsight for establishing the line of fire of a gun comprising; a cathode ray tube for providing a reference mark, optical means for imposing an image of said mark in the line of sight of a gunner whereby the image may be viewed simultaneously with a target, means responsive to movement of the sight in the plane of train for providing an electrical signal proportional to the rate of movement of the gunsight in train, means responsive to movement of the sight in the plane of elevation to provide an electrical signal proportional to the rate of movement of the gunsight in elevation, means for amplifying said electrical signals, means for applying the amplified signals to 18 the cathode ray tube for displacing the reference mark upon movement of the gunsight, means for modifying said electrical signals to compensate for changes in the target range, and means linking the gunsight and the gun for movement together in train and in elevation.

2. An automatic compensating gunsight for establishing the line of fire of a gun comprising; a cathode ray tube for providing a reference mark, optical means for imposing an image of said mark in the line of sight of a gunner whereby the image may be viewed simultaneously with a target, means responsive to the movement of the gunsight in the plane'of train for providing an electrical signal of a value functionally related to the rate of said movement, means responsive to movement of the gunsight in the plane of elevation for providing an electrical signal functionally related to the rate of said movement, means for changing the value of the signals so obtained, means for applying the changed signals to the elements of the cathode ray tube for displacing the reference mark upon movement of the gunsight, means for modifying said electrical signals to compensate for variations in the target range, and means linking the gunsight and the gun for movement together in train and in elevation.

- PHILLIP ROOD WHEELER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,067,859 Bacon et al July 22, 1913 1,322,153 Wilson et al Nov. 18, 1919 1,724,093 Kauch et al Aug. 13, 1929 1,960,333 DuMont May 29, 1934 2,182,530 Alkan Dec. 19, 1939 2,344,296 Frink Mar. 14, 1944 FOREIGN PATENTS Number Country Date 772,998 France Aug. 25, 1934 784,849 France May 6, 1935 480,185 Great Britain Feb. 18, 1938 

